BIOTIC

BIOTIC Species Information for Abra alba
All Taxonomy Biology Distribution Reproduction

Researched by	Lizzie Tyler	Data supplied by	University of Sheffield
Refereed by	This information is not refereed.
Distribution and Habitat
Distribution in Britain & Ireland	Widespread around the British Isles.
Global distribution	Abra alba is distributed from the Norwegian Sea and the Baltic, south to the Iberian Peninsula, into the Mediterranean and Black Seas, and south along the coast of Africa to Senegal.
Biogeographic range	Not researched	Depth range	0 - 60 m
Migratory	Non-migratory / Resident
Distribution Additional Information	Dispersal of post-larval bivalve molluscs The mechanism termed 'byssus drifting' has been observed in 20 species of bivalve molluscs, including Abra alba, and is the mechanism by which post-larval bivalves enter a second pelagic migratory stage. Young bivalves secrete a single, long thread which increases the drag acting upon them and enables them to be carried along on the current. The drag increase was found to be a factor of 3 to 30 times greater on byssus secreting bivalves than on inactive ones (Sigurdsson et al., 1976). Abra alba were observed to re-enter the water column after larval settlement in the Bay of Seine (Olivier et al., 1996). The post-larvae and juveniles of Abra alba were most abundant at flood tide velocities . Furthermore, Abra alba were found to vary significantly in their vertical distribution in the water column, the species decreasing in abundance with distance from the sea bed. It was noted that Abra alba juveniles can regulate their vertical position in the flow, to some extent, by opening their valves to different extents (Olivier et al., 1996).

Substratum preferences	Muddy gravel Sandy mud Mud Muddy sand	Physiographic preferences	Open coast Offshore seabed Strait / sound Sealoch Enclosed coast / Embayment
Biological zone	Sublittoral Fringe Upper Infralittoral Lower Infralittoral Upper Circalittoral Lower Circalittoral	Wave exposure	Sheltered
Tidal stream strength/Water flow	Weak (<1 kn)	Salinity	Full (30-40 psu)
Habitat Preferences Additional Information
Distribution References	Tebble, 1976, Sigurdsson et al., 1976, JNCC, 1999, NBN, 2002, Picton & Costello, 1998, Olivier et al., 1996,